I couldn't figure out how to get to the customizer by keyboard in 3.4.2. I can action the customizer link, but focus moves to the preview pane and no amount of tabs seems to get me to the customizer controls.

22682.diff​ forces the redirect - fixing the issue. Before this, if you edited a field and closed without saving, then went back into the customizer, all of your changes were lost anyway - so it doesn't look as though we're losing anything by forcing a redirect all of the time. Koopersmith may think differently. :-)

22682.diff​ isn't testing well for me. If I use the keyboard to navigate to the Customizer, hit Enter on the close button, and then try to go back to the Customizer by keyboard, it wont load. I can't reproduce that problem by mouse, and the problem goes away when I remove the patch or disable script debug.

22682.diff​ isn't testing well for me. If I use the keyboard to navigate to the Customizer, hit Enter on the close button, and then try to go back to the Customizer by keyboard, it wont load. I can't reproduce that problem by mouse, and the problem goes away when I remove the patch or disable script debug.

Yep, good catch. I was able to replicate what you're seeing. This is a weird little bug.